cut on both strokes have not been highly appreciated by users.
Whitworth used a circular tool-box to his planing machines, and the
tool-point was automatically moved through 180° after each stroke
by cords and pulleys, much as the plate-planer tool is now moved
(see c, Fig. 285, p. 295). Lack of rigidity caused the abandon-
ment of this tool for good machines, however. Two recent double-
acting tools, by Messrs. J. Buckton & Co., are shewn in Fig. 784.
The tool A is suited to a slotting machine, and is automatically
reversed by rod B, on which are tappets. The main difficulty
here, and whenever one tool has two edges, is the difficulty of
sharpening symmetrically. The planing tool-box c is an improve-
ment in this respect, for both tools can easily be set at their
proper heights. The tools are fixed in slots made in discs, so
that when one tool is at work the other trails on the return, the
spring D keeping the acting tool to its cut. Both arrangements
are said to work very well in practice.
Facing Head.—Small articles such as pipe flanges are very
economically surfaced in a drilling machine by adopting a facing
head as in Fig. 785. It is fixed to the spindle by a coned shank
and collar as usual, and a radial feed is given to the tool-box D by
the star B and screw c, the former striking a fixed projection at
every revolution of the spindle.
P. 200. Turret-head Lathe with vertical Mandrel.—
The special tool shewn in Fig. 785^ is called by its designers,,
the Richards Machine Tool Co., a ' Universal Turning Machine/
but is apparently better described as above. It may be under-
stood by a reference to the description on p. 200. The mandrel
is supported on a footstep, and driven by worm gear, and there
are two vertical slides corresponding to a lathe saddle and slide
rest. The turret is shewn provided with tools for turning piston
rings from a cylindrical casting, for which purpose a turns the top,.
b roughs the thickness which c finishes, and d parts to correct,
width. For the last operation the tools are gradually fed through
the work by turning the hand wheel e. (Seej>. 978.)
P. 212. Originating a Surface Plate. — Mr. W. BL